Artifical tanning substance



Patented May 11 1926.

' i UNITED STATES 1,5 3,801v PATENT-OFFICE. j

OTTO SCHMIDT, OF LUD'WIGSHAFEN-ON-THE-iR-HINE, GERMANY, .ASS IG-NOR TOBADISCHE ANILIN- & SODA-FABRIK,' F LUDWIGSHAFEN-ON THE-RHINE, GER-'MANY, n'conronA'rroN or GERMANY.

ARTIFICIAL TANNING SUBSTANCE. I

1N0 Drawing.

This present invention relates to improvements in the preparation ofartificial tanning substances,

It is already known that by treating 5 charred vegetable materials suchas charcoal 1 with nitric acid or nitrogen oxids substances possessingtanning properties are obtained.

I have now found that the tanning properties of these substances are.much improved by bringing them into a weakly acid condition. This resultmay be obtainedby neutralizing them partially or wholly and againslightly acidulfiting them. Preferably, the products are neutralized toabout to 40 per cent ;v any other degree of neutralization, however, mayalso be suitable.

hen tanning substances prepared 'according to this invention are usedthe advantage that the hides do not swell too much 20 from thecommencement of the operation re- 1 suite and the tanning process isthereby accelerated and the hides tanned more thorbnghly. The color ofthe leather is also better and lighter by reason of the hides notswelling so much as aforesaid. I

I I have furth r found that especially good tanning substances areobtained by oxidizing charcoal containing an unusual quantity of oxygencompounds and then partially-neutralizing the product. Such charcoalsas.

contain 9 percent or more of oxygen, calculated on the coaly substancefree from ashes, are especially sultable, yielding with amoderateconsumption of nitric acid or nitrogen as oxids tanning substances of aremarka ly.

light-color. It is generally sufiicient to neutralize a. small fractionof the acidity of the product.

The said substances can be mixed, before 40 or after reducing theiracidity, with other artificial tanning substances, such for ex" 4 ampleas formaldehyde-naphthalene-sulfonic acid condensation products on theirsal ts, orotherartificial tanning substances containing one or severalsulfonic' acid groups, or their salts.' They can also be mixed with veetable tanning substances such, for e-xamp e, as quebracho and the like.With such a combination, and especially that with ve etable tanningmatters, the

grainof the. eather will keepflmuch better than in the case of leathertanned by mix- .tures-with the raw oxidation products pos Applicationfiled August 24, 1925. Serial No. 52,233.,

sessing no reduced acidity," in the lattercasc.

the grain is often brittle.

The nature of this invention is more fully '5 explained by the followingexamples to which however the invention is not restricted. The parts areby weight.

I Example 1.

20 parts of a dry tanning substance, obtained by oxidizing. charcoalwith nitric acid, possessing an acidity equal to about 10 cubiccentimetres of normal caustic soda liquor to l'gram of the substance,are dissolved in 80 parts of-water and mixed with 40 parts of normalcaustic soda.

280'parts of the tanning solution soprepared are diluted with water to1000 parts by volume. Into this tanning bath 60 parts of well delimedhide are introduced. The hide is tanned in the course of 8 to 10 daysand a full, soft leather of a red-brown color is obtained.

Example 2.

140 parts by weight of the solution prepared as described in the firstparagraph of Example 1 are mixed with parts of chestnut-wood extract andthen diluted with water to 1000 parts b volume. About 60 parts ofcarefullyde imed hide are tanned" in this bath in the usual manner in 10to 14 days. A light-brown full leather with stable grains is obtained. v

The tanning oxidation product ma be prepared as follows: parts of elypowdered charcoal with an oxygen content of 14.8 per cent,-'calculatedon ash-free sub.- stance, are stirred'with 160 parts of water. parts ofa95 per cent nitric acid 'solution are then slowly added whereupon themass is slowly heated to the boil. After boilingfor 12 hours the greaterpart of the 95 liquid is-distilled oif and'680 more parts of a.95 percent nitric acid solution are added while continuing boiling for twodays. The mainpartof the aqueous nitric acid left in the vessel isdistilled 0s, employing finally 1 a vacuum, and for removin the lasttraces of nitric acid an addition 0 water is made repeatedly withsubsequent evaporation.

The residue is powdered, giving an orange to ellowishpowder which iscompletely solu le in water and has excellent properties. Instead ofnitric acid, nitrogen oxid may be employed.

I claim:

1. As an article of manufacture an oxidation product of charcoalpossessing tanning properties and being partly in the form of an acidand partly in the form of a soluble salt. v

2. Asi1n article of manufacture an oxidation product of charcoalpossessing tanning properties and being partly in the form of an acidand partly, in the form of a soluble salt in combination with anothertanning material.

3. The process of prodncingtanning materials which consists in acting oncharcoalwith a nitric acid solution and partly neutraliz ng theoxidation product with a baseforming a soluble salt.

4. The process of producing tanning materials which consists inoxidizing a charcoal containing at least 9 per cent of oxygen,calculated on the coaly substance free from ashes with nitric acid andpartly neutralizing the oxidation product with a base forming a solublesalt.

The process of producing tanning ma terials which consists in oxidizinga charcoal containing at. least 9 per cent of oxygen, calculated on thecoaly substance free from ashes with nitric acid, partly neutralizingthe oxidation product with a baseforming a soluble salt, and mixing theproduct with 'a natural tanning extract.

In testimony whereof I have hereunto set my hand.

OTTO SCHMIDT.

